Motor fuels containing keto carboxylic acids



3,074,787 MOTGR FUELS CGNTAINTNG KETO CARBGXYLIC AQHDS George W. Eckert, Wappingers Falls, and Howard V.

Hess, Glenham, N.Y., assignors to Texaco Inc., a corporation of Delaware No Drawing. Filed Dec. 2, 1957, Ser. No. 699,943 9 (Jlaims. (Cl. 44-69) This invention relates to a hydrocarbon fuel composition of high octane rating. More specifically, it involves the discovery that the octane rating of leaded gasoline fuels is substantially improved by the addition of keto carboxylic acids.

The recent increase in compression ratios of automobile engines have placed a severe train on petroleum refiners to produce fuels having the octane rating demanded by these engines. Premium fuels at the present time have research octane ratings between 97 and 100 and it has been predicted that premium fuels will have to have octane ratings between 105 and 110 five years from now in order to satisfy the octane requirements of the high compression automotive engines predicted for that date. In order to produce premium fuels of octane ratings of 95 and above, it has been necessary for refiners to rely heavily on catalytic refining operations such as fluid catalystic cracking, catalytic reforming, alkylation and catalytic isomerization.

Catalytic cracking and catalytic reforming, which are the most widely used refining operations in the production of high octane fuels, produce substantial quantities of aromatics; catalytic cracking also produces a substantial amount of olefins. it is well known that olefins and aromatics, although possessing high octane ratings, have a poorer response to organo-lead compound such as tetraethyl lead than saturated aliphatic gasoline components. Accordingly, as the aromatic and olefinic content of the gasolines have increased to meet the octane levels required by modern automotive high compression engines, the lead response of the resulting fuels has diminished.

Stated another way, the octane increment obtainable by the addition of an organo-lead compound decreases as the aromatic and olefin contents of the base fuel increase. The subject invention involves the discovery that the octane rating of leaded motor fuels containing a substantial concentration of high octane components, that is, aromatics, olefins and mixtures thereof, is markedly im- I proved by the addition of a small amount of a keto-substituted monocarboxylic acid.

In copending application Serial No. 689,466 filed October 11, 1957, it is disclosed that monocarboxylic acids in prescribed concentration substantially raise the octane rating of a motor fuel containing an organo-lead antiknock agent and a substantial concentration of high octane components which may be aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereoffl The subject invention involves the discovery that monocarboxylic acids containing a keto group exert a similar anti-knocked action in motor fuel compositions of the prescribed type.

The high octane hydrocarbon motor fuel of this invention comprises high octane components including a substantial concentration of aromatic hydrocarbons, olefinic hydrocarbons, or mixtures thereof, an organo-lead antiknock agent and a keto-substituted monocarboxylic acid in a concentration of at least 0.1 volume percent of the fuel.

The action of keto-substituted monocarboxylic acids in raising the octane rating of gasoline is characterized by several unusual features. In the first instance, the keto carboxylic acids appear to be ineffective in raising the octane rating of gasolines unless an organo-lead anti-knock agent, normally tetraethyl lead, is a component of the gasoline mixture.

The second unusual characteristic of the action of ketosubstituted monocarboxylic acids in appreciating the octane rating of gasolines is the fact that equal concentrations of acids appear to cause a greater octane improvement above the 100 octane level than below the 100 octane level. The third unusual feature of the action of keto-substituted monocarboxylic acids is that they appear to have substantially no effect on the octane rating of a gasoline consisting essentially of saturated aliphatic hydrocarbons even though an organo-lead anti-knock agent is present. Since organo-lead anti-knock agents exert their greatest octane appreciation in predominantly saturated parafiinic base hydrocarbon gasolines and have the least effect on the octane rating of aromatic and olefin rich gasolines, the present invention neatly complements tetraethyl lead as an octane improver. Keto-substituted monocarboxylic acids have their minimum effect where tetraethyl lead has its maximum effect and exert their maximum effect on octane values where tetraethyl lead has its minimum effect.

The novel fuel compositions of this invention have a minimum concentration of aromatic and, or olefin components of at least 10 volume percent. The aromatic and/ or olefin components of the motor fuel of the invention can constitute as high as 100 volume percent thereof but usually comprise between 20 and volume percent. The minimum 10 percent concentration is necessary for keto-substituted monocarboxylic acids to exert a significant octane improvement.

The aromatic components of the motor fuel of the invention are generally supplied by catalytic reforming or catalytic cracking operations. Catalytic reformate is particularly high in aromatics. The olefin components of the motor fuel of the invention are derived either from thermal cracking, catalytic cracking or polymerization.

The organo-lead reagent necessary for the action of keto-substituted monocarboxylic acids as octane irnprovers is a tetraalkyl lead compound of the class known to possess anti-knock action. Tetraethyl lead is Practically universally used as an anti-knock agent but other tetraalkyl lead compounds such as tetramethyl lead, tetrabutyl lead, tetraamyl lead, tetrapropyl lead, etc. are known to possess anti-knock properties and may be used in the fuel compositions of the invention in conjunction with ketosubstituted monocarboxylic acids.

The tetraethyl lead mixtures commercially available for automotive use contain an ethylene chloride-ethylene bromide mixture as a scavenger for removing lead from the combustion chamber in the form of volatile lead halides. As is used hereafter in the examples illustrating the invention, tetraethyl lead fluid denotes the commercial product which comprises tetraethyl lead, ethylene chloride and ethylene bromide, the latter two reagents being present in 1.0 theory and 0.5 theory respectively, theory denoting the stoichiometric amount required for reaction with the lead content of the tetraethyl lead.

The organo-lead reagent is present in the fuel compositions of the invention in concentrations between 0.5 ml. per gallon up to the statutory limit of organo-lea'd reagent concentration which, at the present time, is 3 ml. per gallon in the case of automotive fuel and 4.6 ml. per gallon in the case of aviation fuel. The usual'concentration of tetraethyl lead is between 1 and 3 ml. per gallon in automotive gasoline and 2-4.6 ml. per gallon in aviation gasoline.

The keto-substituted monocarboxylic acids which are effective in increasing the octane rating of an aromatic and/ or olefin-containing gasoline in the presence of an organo-lead anti-knock agent contain 430 carbon atoms. The keto acids have the general formulas wherein R is a monovalent hydrocarbyl radical containing 1-27 carbon atoms and R is a divalent hydrocarbyl radical containing 1-l8 carbon atoms. Aliphatic keto monocarboxylic acids, cyclo aliphatic keto monocarboxylic acids, and aromatic keto monocarboxylic acids are all effective anti-knock agents in leaded fuels containing a substantial aromatic and/or olefin content. Keto-substi-tuted monocarboxylic acids effective as octane appreciators in the fuel compositions of the invention are the following: levulinic acid, 4-ketostearic acid, 3-oxo-n-hexanoic acid, -4-oxo-2-ethylhexanoic acid, 5-phenyl-3-oxopentanoic acid, 3-phenyl-3-oxopropanoic acid and 6-oxododecanoic acid.

The preferred keto acids used in the fuel compositions of the invention contain 414 carbon atoms and are aliphatic in nature. Levulinic acid and 4-ketostearic acid are preferred keto acids for use in the fuel compositions of the invention.

The effectiveness of keto carboxylic acids in raising the octane rating of leaded fuels containing an aromatic: and/ or olefin content is surprising in view of the fact that other substituted monocarboxylic acids such as hydroxy monocarboxylic acids, halogenated monocarboxylic acids and sulfhydryl-substituted monocarboxylic acids are ineffective as anti-knock agents in the fuel compositions of the invention.

The keto-substituted monocarboxylic acids must be present in the leaded aromatic and/or olefin-containing compositions of the invention in a minimum concentration of 0.1 volume percent before a significant octane appreciation is realized. When keto acid concentration is below 0.1 volume percent, no octane improvement is obtained in leaded gasoline containing 10 or more volume percent aromatics and/ or olefins. The preferred concentration of keto-substituted monocarboxylic acid in the fuel compositions of the invention falls between 0.2 and 1.0 volume percent with maximum octane appreciation generally being obtained at a concentration level of about 0.5 volume percent. Concentrations of keto-substituted monocarboxylic acids as high as 5 volume percent can be incorporated in the fuel compositions but no additional octane improvement is realized at the higher concentrations and economic considerations preclude the use of such concentrations in commercial fuel compositions.

In the following table there is shown the action of keto carboxylic acids in raising the octane rating of the leaded fuel compositions of the invention. The base fuel to which the keto acids were added in a concentration of about 0.5 volume percent was a catalytically reformed naphtha containing 3 cc. of tetraethyl lead fluid per gallon and having an IBP of 130 F. and an end point of 394 F. The base fuel had a leaded research octane rating of 96.6 and an aromatic concentration of 48 volume percent as measured by fluorescent indicator analysis (FIA) method.

Table I Research octane number Base fuel 96.6 Base fuel +0.25 V. percent levulinic acid 97.6 Base fuel +0.5 v. percent levulinic acid 97.8 Base fuel +0.25 v. percent 4-ketostearic acid 97.2

Base fuel +0.50 v. percent 4-ketostearic acid 97.2 Base fuel +0.5 v. percent mono-chloroacetic acid 87.0 Base fuel +0.5 v. percent heptafiuoroacetic acid 89.3 Base fuel +0.5 v. percent 2-bromohexanoic acid 96.3

Base fuel +0.5 v. percent mercaptoacetic acid 96.0 Base fuel +0.5 v. percent ricinoleic acid 966 Base fuel +0.5 v. percent salicylic acid 96.6

The foregoing data demonstrate very clearly the elfec: tiveness of the prescribed concentration of keto acids in raising the octane rating of a leaded gasoline having a prescribed aromatic content. The improvement in octane rating obtained by the addition of levulinic acid and 4 ketostearic acid in concentrations between 0.25 and 0.5 volume percent is significant at the 96 octane level.

The data in the table also indicate the specificity of keto acids in raising the octane rating of leaded fuels containing an aromatic and/or olefin content. While the keto acids raise the octane rating of the base fuel more than 1 unit on the research octane scale, halogenated acids, hydroxy acids and mercapto acids either had no effect or substantially decreased the octane rating of the leaded catalytic reformatc.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing an organo-lead anti-knock agent, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in a concentration of at least 10 volume percent, and a keto-substituted hydrocaroyl monocarboxylic acid con taining 4 to 30 carbon atoms, said keto acid being present in a concentration between 0.1 and 5.0 volume percent, which concentration is sufiicient to effect substantial improvement of the octane rating of said hydrocarbon fuel.

2. A hydrocarbon fuel according to claim 1 in which said keto-substituted monocarboxylic acid has the gen- .eral formula selected from the group consisting of O l U RCOOH and RCRCOOH :in which R is a monovalent hydrocarbyl radical containing 1-27 carbon atoms and R is a divalent hydrotcarbyl radical containing 1-18 carbon atoms.

3. A hydrocarbon fuel according to claim 1 in which :said organo-lead anti-knock agent is present in a concentration between 0.5 and 4.6 cc. per gallon.

4. A hydrocarbon fuel in the gasoline boiling range containing a tetraalkyl lead anti-knock agent in a concentration of at least 0.5 cc. per gallon, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof in a concentration of at least 10 volume percent of said fuel and a keto-substituted monocarboxylic acid having the general formula selected from the group consisting of in which R is a monovalent hydrocarbyl radical containing 1-27 carbon atoms and R is a divalent hydrocarbyl radical containing 1-18 carbon atoms in a concentration of 0.1 to 5.0 volume percent.

5. A hydrocarbon fuel according to claim 4 in which the concentration of said keto acid is between 0.2 and References Cited in the file of this patent UNITED STATES PATENTS Orelup et al. Nov. 20, 1928 Conquest Nov. 23, 1937 (Other references on following page) UNITED STATES PATENTS Lipkin Aug. 13, 1940 Cox Ian. 7, 1941 Kleinholz Jan. 26, 1954 FOREIGN PATENTS France Mar. 26, 1928 France Dec. 2, 1935 France Feb. 23, 1939 6 277,326 Great Britain Jan. 7, 1929 599,222 Great Britain Mar. 8, 1948 OTHER REFERENCES Aviation Gasoline Manufacture, by Van Winkle, first ed., 1944, McGraW-Hill Co., pages 200-205 and 212- 223.

Improved Motor Fuels Through Selective Blending, by Wagner et al., paper presented before American Pe- France June 1, 1955 10 troleum Institute, Nov. 7, 1941. 

1. A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE CONTAINING AN ORGANNO-LEAD ANTI-KNOCK AGENT, HIGH OCTANE COMPONENTS SELECTED FROM THE GROUP CONSISTING OF OLEFINIC HYDROCARBONS, AROMATIC HYDROCARBONS AND MIXTURES THEREOF IN A CONCENTRATION OF AT LEAST 10 VOLUME PERCENT, AND A KETO-SUBSTITUTED HYDROCARBYL MONOCARBOXYLIC ACID CONTAINING 4 TO 30 CARBON ATOMS, SAID KETO ACID BEING PERSENT IN A CONCENTRATION BETWEEN 0.1 AND 5.0 VOLUME PERCENT, WHICH CONCENTRATION IS SUFFICIENT TO EFFECT SUBSTANTIAL IMPPROVEMENT OF THE OCTANE RATING OF SAID HYDROCARBON FUEL. 